Hot extrusion is a process in which wrought parts are formed by forcing a heated billet through a shaped die opening. This article discusses nonlubricated and lubricated hot extrusion. The two nonlubricated hot extrusion methods are forward or direct extrusion and backward or indirect extrusion. The article illustrates the significance of extrusion speeds and temperatures in hot extrusion. It describes the basic types of presses used in the hot extrusion of metals. The article provides information on the characterization of extruded shapes and explains the operating parameters, including extrusion velocity, amount of pressure required, and type of lubricant, for successful and efficient hot extrusion. The article concludes with a discussion on applications and design methodology that provides insight into CAD/CAM of extrusion dies.

This article describes the direct hot extrusion process and the typical sequence of operations for producing extruded aluminum shapes from soft and medium-grade aluminum alloys, hard alloys, and aluminum-matrix composites. It discusses key process variables, including extrusion speed and exit temperature, and their effect on product quality. The article also provides information on extrusion presses, press dies, and tooling, and addresses quality issues such as surface defects, blistering, and internal cracking. It concludes with a discussion on the drawing of solid section and aluminum tube.

This article discusses two basic forms of extrusion: cold and hot. It provides information on three types of extrusion processes, namely, direct extrusion, reverse extrusion, and hydrostatic extrusion. The article also discusses the mechanics, analysis, tooling and die design of extrusion as well as thermodynamics. The finite-element method suitable for simulation of metal forming processes is explained. The article examines the extrusion defects that are divided into three different categories including surface, subsurface, and internal type. It includes information on friction and lubrication modeling of extrusion processes. The article also discusses the fundamentals of extrusion technology of titanium alloys and aluminum. It concludes with information on two forms of wear in extrusion, namely, adhesive and abrasive wear.

Aluminum and aluminum alloys are very suitable for extrusion and many types of profiles can be produced from easily extrudable alloys. This article lists the basic characteristics of aluminum and its alloys. It tabulates the aluminum extrusion alloys by series and lists the typical applications for 6xxx series aluminum extrusions. The article discusses three broad categories of extrusion profiles: solid profile, hollow profile, and semi hollow profile. It provides information on weldability and machinability, which are often considered in profile design and product performance. The article discusses different aluminum extrusion processes, such as the direct extrusion process and the indirect extrusion process. It schematically illustrates the plotting of flow stress and extrudability for several types of aluminum alloys. The article concludes with information on the heat treatment and precipitation hardening for alloys, such as 2xxx, 6xxx, and 7xxx.

Workability is the ability of the workpiece metal to undergo extrusion or drawing without fracture or defect development. This article describes the limits of workability in extrusion and drawing in terms of fracture and flaw development and presents some comments on fracture mechanisms. It discusses the empirical projections of absolute workability from various mechanical tests. The article concludes with a discussion on extrusion and drawing process design implications.

This article describes the mechanics and processing characteristics of equal-channel angular extrusion (ECAE). Tool design considerations for the ECAE are discussed. During ECAE, severe plastic strains and simple shear deformation mode contribute to strong, sometimes unusual effects of processing on structure and properties. The article explains these effects and concludes with a discussion on the applications of the ECAE.

This article lists functions of lubricants common to the majority of applications and processes. It discusses the lubricant candidates widely used in forging: conversion coatings with soaps (stearate compounds) and molybdenum disulfide for cold forging; oil-based thick, film oil or polymerbased lubricants and molybdenum disulfide for warm application; graphite suspensions in oil or water for hot forging steels; and glass films for titanium and superalloys hot forgings. The article describes the applications of lubricants in warm extrusion and forging, hot forging of steel, hot forging of aluminum, isothermal and hot die forging, and the extrusion of steel.

This article focuses on direct extrusion processing where metal powders undergo plastic deformation, usually at an elevated temperature, to produce a densified and elongated form having structural integrity. It provides information on the basic powder extrusion processes and the mechanics of extrusion. The article also examines specific extrusion practices for the production of wrought material from powder stock and provides examples of materials processed by powder extrusion.

In general, metal-matrix composites (MMCs) are classified into three broad categories: continuous fiber-reinforced composites, discontinuous or short fiber-reinforced composites, and particle-reinforced composites. This article focuses on stir casting and melt infiltration as the two main methods of MMC solidification processing. It describes the MCC casting methods, such as sand and permanent mold casting, centrifugal casting, compocasting, and high-pressure die casting. The article discusses the MMC infiltration processes in terms of pressure infiltration casting and liquid metal infiltration. It reviews the powder metallurgy processing of aluminum MMCs and deformation processing of discontinuously reinforced aluminum composites. The article concludes with a discussion on the processing of fiber-reinforced aluminum.

This article describes the effects of furnace atmospheric elements, including air, water vapor, molecular nitrogen, carbon dioxide, and carbon monoxide, on steels. It provides useful information on six groups of commercially important prepared atmospheres classified by the American Gas Association on the basis of the method of preparation or on the original constituents employed. These groups are designated and defined as follows: Class 100, exothermic base; Class 200, prepared nitrogen base; Class 300, endothermic base; Class 400, charcoal base; Class 500, exothermic-endothermic base; and Class 600, ammonia base. These are subclassified and numerically designated to indicate variations in the method by which they are prepared. The article also contains a table that lists significant furnace atmospheres and typical applications.

Coextrusion is defined as the simultaneous extrusion of two or more metals to form an integral product that can be carried out using conventional extrusion or drawing equipment at a temperature appropriate to the metal system being formed. This article discusses the applications, billet configurations, and metal flow modes of coextrusion. It presents the analytical studies of coextrusion: deformation energy methods, lower-bound (slab) analyses, upper-bound analyses, and finite-element analyses. These studies are used to identify the regime of material properties and process variables for which sound extrusions can be obtained. The article concludes with a discussion on the state-of-the-art of coextrusion that assists in developing process models, which accurately describe both the macroscopic and microscopic aspects of a process.

This article describes the extrusion process, which converts soft, plastic material into a particular form using an extruder, or screw conveyer. It discusses the two main types of plastic extruders, twin-screw and single-screw, estimation of extruder capacity, and design and operations (heating, cooling, downstream sizing, corrugating, and crossheading) of the screw, the most important component of any extruder. It discusses the shapes produced by screw extrusion and the types of extrusion products produced by extrusion processes, including blown-film extrusion, flat-film or sheet extrusion, chill-roll film extrusion, pipe or tube extrusion, wire and cable coverings, extrusion coating, and profile extrusion, and provides some discussion on multiple-screw extruders. The article describes the dimensional accuracy of extrusion products, and lists common defects that occur frequently in the extrusion process.

Niobium-titanium alloys (NbTi) became the superconductors of choice in the early 1960s, providing a viable alternative to the A-15 compounds and less ductile alloys of niobium-zirconium. This can be attributed to the relative ease of fabrication, better electrical properties, and greater compatibility with copper stabilizing materials. This article discusses the ramifications of design requirements, selection criteria and processing methods of superconducting fibers and matrix materials. It provides information on the various steps involved in the fabrication of superconducting composites, including assembly, welding, isostatic compaction, extrusion, wire drawing, twisting, and final sizing. The article also provides a detailed account of the properties and applications of NbTi superconducting composites.

Cold extrusion is a push-through compressive forming process with the starting material (billet/slug) at room temperature. This article provides information on the different types of steels that can be cold extruded. Mechanical presses and hydraulic presses that are specifically designed for cold extrusion with high rigidity, accurate alignment, and long working strokes are described. The article details the factors that are critical in cold extrusion: punch design, die design, and tool design. It summarizes the role of lubricants during extrusion of steel, such as soap lubricant and polymer lubricants. The article describes several procedures for extruding specific steel parts such as tubular parts and stepped shafts. It lists problems such as tool breakage and galling or scoring of tools and explains cold extrusion of aluminum, copper, and nickel alloy parts. The article also discusses the impact extrusion of magnesium alloys.

Tool steels are carbon, alloy, and high-speed steels that can be hardened and tempered to high hardness and strength values. This article discusses the classifications of commonly used tool steels: water-hardening tool steels, shock-resisting tool steels, cold-work tool steels, and hot-work tool steels. It describes four basic mechanisms of tool steel wear: abrasion, adhesion, corrosion, and contact fatigue wear. The article describes the factors to be considered in the selection of lubrication systems for tool steel applications. It also discusses the surface treatments for tool steels: carburizing, nitriding, ion or plasma nitriding, oxidation, boriding, plating, chemical vapor deposition, and physical vapor deposition. The article describes the properties of high-speed tool steels. It summarizes the important attributes required of dies and the properties of the various materials that make them suitable for particular applications. The article concludes by providing information on abrasive wear and grindability of powder metallurgy steels.

Material extrusion systems are the most common types of additive manufacturing systems, also known as three-dimensional (3D) printers. This article focuses on the general 3D printing processes as can be demonstrated and manipulated in desktop printers. The discussion includes details of the components involved in material extrusion as well as the melt extrusion solidification (during cooling) process, the underlying mechanism of road bonding, and the factors affecting good part quality. The discussion also covers support material, postprocessing, and road-quality considerations and the addition of infill in melt extrusion to the hollow spaces inside an object to give it structural strength. Information is also provided on different materials and associated material properties that affect the rate the printer is able to advance and retract material, thereby affecting the quality and rate at which a part is printed. The final section provides information on the mechanism of viscous extrusion 3D printing.

Aluminum products such as fasteners and automotive components are often produced by cold extrusion because it facilitates high volume production of near-net-shape parts. This article describes the cold extrusion process for aluminum alloys and the associated requirements for tooling, dies, punches, and other equipment. It covers typical tool materials and their working properties, and provides best practices for sizing aluminum slugs and preparing them for use. The article also discusses the wide range of achievable shapes from shallow cup-like extrusions to deep cups and complex parts with longitudinal flutes, stems, and grooves.

Cold heading is typically a high-speed process where a blank is progressively moved through a multi-station machine. This article discusses various cold heading process parameters, such as upset length ratio, upset diameter ratio, upset strain, and process sequence design. It describes the various components of a cold-heading machine and the tools used in the cold heading process. These include headers, transfer headers, bolt makers, nut formers, and parts formers. The article explains the operations required for preparing stock for cold heading, including heat treating, drawing to size, machining, descaling, cutting to length, and lubricating. It lists the advantages of the cold heading over machining. Materials selection criteria for dies and punches in cold heading are also described. The article provides examples that demonstrate tolerance capabilities and show dimensional variations obtained in production runs of specific cold-headed products. It concludes with a discussion on the applications of warm heading.

This article discusses the dies, such as shear-face dies, conical-feed dies, and bridge dies, that are used in extrusion of particle-reinforced aluminum composites. It provides an overview of the effects of reinforcements on the properties of aluminum composites.

Forging machines use a wide variety of hammers, presses, and dies to produce products with the desired shape, size, and geometry. This article discusses the major types of hammers (gravity-drop, power-drop, high speed, and open-die forging), and presses (mechanical, hydraulic, screw-type, and multiple-ram). It further discusses the technologies used in the design of dies, terminology, and materials selection for dies for the most common hot-forging processes, particularly those using vertical presses, hammers, and horizontal forging machines. A brief section is included on computer-aided design in the forging industry. Additionally, the article reviews specific characteristics, process limitations, advantages, and disadvantages of the most common forging processes, namely hot upset forging, roll forging, radial forging, rotary forging, isothermal and hot-die forging, precision forging, and cold forging.